The invention relates to a method for fitting cables with cable sleeves, and to a transfer unit.
A cable sleeve or “seal” is a complex plastic ring with several radial expansions (“shoulders”), which is slipped over an insulated cable harness, and seals the cable harness (e.g., a multi-core strand) or each individual cable of a cable harness with one or more crimped-on contacts against the penetration of liquid and contaminants.
The process of mounting seals on cables in cable processing plants is today fully automated. In particular, there are also largely autonomous and compact processing stations with standardized interfaces, that execute the process of fitting cables with seals as part of a multistage, fully automated cable processing routine (e.g., stripping before and crimping after seal assembly), and make it possible to modularly expand all automated cable processors available on the market with an additional seal fitting station.
The main processing steps involved in the typical machining of seals include: a.) conveying them out of a storage container onto a conveyor (conveyor belt, conveyor rail); b.) separating and orienting them on the conveyor; c.) accommodating them on a holding arbor from the conveyor; d) slipping them onto an assembly pipe; e) guiding them on the assembly pipe over the cable to be fitted; f) and, stripping them from the assembly pipe onto the cable. Published European patent application EP0410416A2 discloses a method wherein a leading bung seal in a magazine is picked up by a bung seal transfer clamp and is positioned between a bung seal receptacle and a bung seal transfer device, which are axially aligned. A bung seal expansion pin is advanced to drive the leading bung seal into the bung seal receptacle, to force it against a resilient grommet therein, and to extend through the bung seal so as to expand it. A bung seal expansion sleeve surrounding the expansion pin is then advanced further to expand the bung seal and the pin is withdrawn leaving the bung seal secured to the expansion sleeve by its own resilience. A lead is then inserted into the expansion sleeve, and the expansion sleeve is then withdrawn, leaving the seal secured to the lead, by its own resilience, after which the bung seal receptacle is opened and the lead with the bung seal thereon is removed to a station at which an electrical terminal is crimped to the lead and to the bung seal.
In order to avoid processing mistakes in this process chain to the greatest extent possible, fault-prone subprocesses are often subjected to fully automated monitoring while processing the seals.
Prior art discloses, in particular, optical monitoring devices (e.g., photoelectric barriers or digital cameras with evaluation electronics) for achieving this objective. For example, in seal stations readily available on the market, a photoelectric barrier checks for the presence of a seal in the position where it is accommodated via the conveyor at a specific point in time or during a specific period within the work cycle time interval. If no seal is detected in the accommodation position, the fitting process is stopped.
Seal orientation is also important for the correct accommodation of a seal via the conveyor, and hence is sometimes monitored.
In the absence of such monitoring, any process errors that arise in this process stage may lead to difficulties as subsequent procedural steps run their course, or yield a seal-fitted cable that does not satisfy the stringent quality requirements set forth in the relevant standards as the end product of the seal fitting process or entire cable processing routine. A cable faultily processed in this way usually ends up as scrap. This not only represents a cost factor, but may also be associated with logistical problems.
The orientation of a seal is understood as the alignment of its axis running centrally through its middle tunnel. This axial direction is adjusted in a seal while conveying it into the accommodation position in such a way that, in the accommodation position, it is preferably parallel to the main axis of the holding arbor provided for accommodating the seal via the conveyor. During proper operation, the seal is oriented and positioned on the conveyor in such a way that the holding arbor punches centrally through the seal during a forward stroke along the tunnel/bore axis of the seal in order to accommodate the seal.
In contrast, the term “orienting a seal on the holding arbor” as used in the following assesses the orientation of a seal generally defined above. If the seal is centrally punched through by the holding arbor along the tunnel axis of the seal during its forward stroke, the seal orientation on the holding arbor is regarded as “correct”, otherwise as “incorrect”.
Assuming that a seal is present in the accommodation position, primarily the following fault scenarios are possible while accommodating a seal, which lead to an erroneous orientation of the seal on the holding arbor in the sense just established:                1) The holding arbor collides with the seal from outside, and maximally penetrates far enough into the jacket body of the seal that the seal does not get caught in the holding arbor. The seal is instead only crimped from outside from the effect exerted by the forward stroke of the holding arbor, with any potential damage only being done to the exterior. In the process, it is                    a) either jammed by the holding arbor and remains in the accommodation area of the conveyor, or            b) forced or catapulted out of the accommodation position by the holding arbor and lost, possibly disrupting the process at another location.                        2) During its forward stroke, the holding arbor at least partially penetrates far enough into the jacket body of the seal that the seal gets caught in the holding arbor. A distinction must here be made between the two cases, in that the holding arbor:                    a) either penetrates into the incorrectly oriented seal from outside, or,            b) after partially introduced into the tunnel of the seal, penetrates or punches through the jacket body of the latter from inside.                        
In all of these errors, the seal already may not be processable further in light of the high probability that the sealing lips of the seal arranged on the inside have become damaged, or the seal no longer satisfies the stringent tightness requirements due to exterior damages. Preventing damages is a common task in most technical fields, as may be observed from, e.g., US 2003/079342 A1. This document discloses a wire manipulator which includes a body with a jack for moving clamping arms to hold a wire extremity insert the extremity in an alveolus of a connector. The insertion force is sensed by a force sensor in the clamping arms and is compared with a reference force to stop the insertion process to avoid damage to the wire, the connector and the manipulator.
The mentioned procedural errors stem from a deficiently aligned seal in the accommodation position on the conveyor. Operators have until now subjected the seal accommodation to occasional visual monitoring so as to be able to respond as directly as possible thereto, even though having to interrupt the process. This personal monitoring Is expensive and unproductive.
Another monitoring procedure involving a photoelectric barrier according to prior art checks the seal in the accommodation position, and is associated with other disadvantages.
While the photoelectric barrier is sufficient for monitoring the presence of a seal in the accommodation position, it provides no information about the correct positioning (location) and orientation of the seal. In general, several photoelectric barriers are needed to monitor the correct positioning and orientation. However, this variant is technically complex, inelegant, and of less robustness. It also delays the overall process of fitting cables with varying seals, since additional setup time must be expended to adjust the position of the photoelectric barriers during each switch between two different seal types.
Monitoring with a digital camera leads to digital snapshots, and analyzing the relevant details of the latter is a time-consuming and computationally intensive process. The wide variety of possible shapes for the seals, for example in terms of their cross section, further raises the complexity of the monitoring camera test algorithms to be processed by the evaluation electronics.
In order to meet the enhanced quality requirements placed on the seal fitting, but also to increase sealing station productivity, it is proving increasingly necessary to shift the monitoring of accommodation position to the process of seal accommodation, at least to the critical phases thereof, and to perform the latter within narrow time intervals, that is, to process ever increasing quantities of test data. The software required for this purpose greatly drives up the price in optical monitoring processes.
However, the time requirements that a high processing clock places on monitoring must be satisfied nonetheless. While this condition poses no problem in inertia-free optical methods involving electronic evaluation, the mechanical steps taken to separate out defective seals should also diminish the work cycle to the least possible extent.
In order to correct processing errors during seal fitting once they have been detected, an incorrectly fitted cable had previously been sorted out after the fact and destroyed. This method reduces the productivity of the fitting system relative to the goal of having the correction take place as proximate in time to the error as possible, and still in the same procedural step whenever possible.